So i took the SAT a couple months ago but got a low school compared to my PSAT. My score was a 1010: 630 in Reading and a 380 in Math.
For the math section, Khan Academy is great; however, I would not be recommended it for reading. With the reading portion it's practice, so print out some practice sections to do. Keep in mind that the grammar skill in the reading section is the easiest, so try to sharpen those skills as much as you can. An essay prep book such as Barrons can be useful.
Khan Academy had tailor-made practice scheduled for the SATs if you need it. You take a diagnostic or placement test and the program will pinpoint what needs work. Then you can follow their steps and watch the videos to learn how to do the different things.
If that doesn’t work, try this app called SAT prep, which has tutors you can hire to help you. Also, it has daily practice problems you can set up to send you each day. That could totally be an option for you.
Best of luck to you!
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Personally, I found that the reading section on Khan Academy helped me improve a lot, whereas the math section did not. It really just depends on your learning needs. Do what works for you:)